The present invention generally relates to a mobile node, an ad hoc network routing controlling method and an ad hoc network system, in which privacy is strongly protected.
As demands for mobile communications are rapidly expanded and diversified, it is required to connect a mobile terminal existing outside an area covered by the nearest mobile communication base station to a mobile communication network. Since it is impossible to directly one-hop-connect such outside mobile terminal even to the nearest base station, a wireless ad hoc network proposal has been made in which such an outside mobile terminal is multi-hop-connected to a base station via other mobile terminal or a temporary simple relaying station. A wireless ad hoc network is a network which is temporarily established by utilizing a mobile terminal or a temporary simple relaying station and the like (See FIG. 1). Each mobile terminal and simple relaying station contain an ad hoc routing protocol, and according thereto each terminal voluntarily exchanges information to establish an ad hoc network. In the ad hoc network, it is important to secure privacy since information can be received by a variety of terminals.
One example of such ad hoc network system is the DSR (Dynamic Source Routing) system in which a new route is established after a mobile terminal generates a routing request. In the DSR system, a transmitting terminal (node) can send data by knowing all node addresses on a route directed to a receiving node. Nodes for relaying the data can understand the next destination to forward to, utilizing forwarded routing information, and therefore the relaying nodes do not contain the routing information, resulting in simple processing. By utilizing the ad hoc network, it becomes possible to provide an outside mobile terminal with cellular communication service, the Internet connecting service and other services. This type of communication system has a gateway node 16 as shown in FIG. 1. The gateway node 16 functions as components in both the ad hoc network and the mobile communication network, and bridges the ad hoc network and the mobile communication network. Any communication node can become a gateway node D. After the gateway node D moves to outside a service area of the mobile communication network, the node cannot be a gateway any longer and becomes just a mobile node.
An ad hoc network is constructed as shown in FIG. 1. Ad hoc networks are not limited to radio communications but can be applied to wired communications also.
A mobile node S(12) establishes an ad hoc network according to an ad hoc routing controlling protocol. In the example shown in FIG. 1, the mobile communication node S(12) is connected to a gateway node D(16) via a relaying node T1(14) and a relaying node T2(15) to establish an ad hoc network. Since the gateway D(16) is in an area covered by a base station B(18), the mobile node S(12) can be connected to the base station B(18) via the gateway node D(16) and enjoy services provided through the base station B(18) (See Patent Document #1).
An example of conventional routing control scheme in the DSR is generally shown in FIGS. 2 and 3. This control scheme is now being discussed in the MANET (Mobile Ad-hoc Networks) Working Group in the IETF (The Internet Engineering Task Force).
With reference to FIGS. 2 and 3, such a conventional routing establishment procedure is explained below. A transmitting node S (Source) shown in FIGS. 2 and 3 corresponds to the mobile node S shown in FIG. 1, but not limited to this and may be a gateway node or other mobile nodes. A receiving node D (Destination) shown in FIGS. 2 and 3 corresponds to the gateway node D shown in FIG. 1, but not limited to this and may be mobile nodes. Relaying nodes T (Transmitter) T1, T2 shown in FIGS. 2 and 3 correspond to the relaying nodes 14, 15 shown in FIG. 1, respectively, but not limited to them. The two relaying nodes T1, T2 shown in FIG. 3 have the same structure and function, and therefore FIG. 2 representatively shows only one relaying node T.
When the transmitting node S starts communication with the receiving node D, a request/reply generator 222 generates a RREQ (Route REQuest) signal that requests ad hoc network routing generation. A transmitter/receiver 226 transmits the RREQ to a network by broadcasting. A transmitting node address ADDS and a receiving node address ADDD are read out from an address storage 227, added to the RREQ, and transmitted together. Such an address may be an IP address, for example. The control message RREQ may contain information relating the upper limitation on the number of hops.
A transmitter/receiver 246 of the relaying node T1 receives the control message RREQ. The relaying node T1 compares the received address ADDD with its own address ADDT1 stored in an address storage 247. If the relaying node T1 finds that the control message RREQ is not directed to itself, then it adds its own address ADDT1 and transmits the control message RREQ by broadcasting.
The relaying node T2 performs a similar forwarding processing.
The receiving node D receives the control message RREQ, and compares the received address ADDD with its own address ADDD stored in an address storage 267. If the receiving node D finds that the control message RREQ is directed to itself, it adds a duplication of the relayed address information to a RREP (Route REPly) message and transmits back to the transmitting node S by uni-casting.
The relaying node T2 receives the RREP. If the relaying node T2 finds its own address in a relaying address list, it forwards this signal by uni-casting.
The relaying node T1 performs similar processing.
The transmitting node S receives the RREP. Based on the combination of address information ADDS and ADDD, the transmitting node S recognizes that this signal is a reply to the RREQ previously sent by itself, and understands the relayed routing information (S-T1-T2-D).
[Patent Document #1] Japanese Laid-open Publication 2003-230167
However, in a conventional DSR ad hoc network system, there is no authentication on the routing control signals RREQ or RREP, and therefore there is a risk that wrong routing control information is adapted. The address information of the transmitting node, the receiving node and the relaying nodes is stored in the header under condition that everyone can read them, and therefore third parties can easily identify the transmitting node and the receiving node, resulting in a privacy problem.